1. Field of the Invention
The present invention relates to a device and method for supporting a substrate.
2. Description of the Related Art
During a photoresist process that is one of semiconductor-manufacturing processes, a resist pattern is formed on semiconductor wafers (hereinafter, referred to simply as wafers) by coating the wafer surface with a resist and exposing the resist to light in the desired pattern, followed by development. Such processing is usually performed using a system that includes a coating/developing apparatus for resist coating/development and an exposure apparatus connected to the coating/developing apparatus.
The coating/developing apparatus includes various modules. These modules are, for example, a resist-coating module for coating each wafer with the resist, a developing module for supplying a developing solution, and a heating or cooling module for heating or cooling the wafer before and/or after processing the wafer in connection with the resist-coating module and the developing module. After that, the wafer is carried between the modules and between the coating/developing apparatus and the exposure apparatus, by, for example, a substrate transport device such as a transport arm, one form of substrate support device for supporting and carrying the wafer. FIGS. 19(a) and 19(b) illustrate an example of a wafer transport section forming a portion of the substrate transport device.
The wafer transport section 101 illustrated in FIGS. 19(a), 19(b) includes a frame 102 formed into generally a C-shape, and the wafer W is retained in such a form as to be surrounded by the frame 102. The frame 102 has a total of four wafer hold sections 103 on its inner surface. The wafer hold sections 103 are each formed from a resin to prevent metal contamination of the wafer W. Each wafer hold section 103 includes a lower-surface support section 104 supporting the wafer W horizontally inside the frame 102. The wafer hold section 103 further includes sidewalls 105 surrounding a periphery of the wafer W and preventing a fall of the wafer W from the wafer transport section 101, and inclined sections 106 arranged. If one peripheral edge of the wafer W gets on one of the inclined sections 106 during wafer transfer or transport, the wafer W will slip downward from the corresponding inclined section 106 and slide along the surface of the lower-surface support section 104. The wafer W will be consequently guided into a support region surrounded by the sidewalls 105.
Although wafer sizes are standardized, a dimensional error ranging between about ±0.25 mm and about ±0.50 mm exists with each wafer. When the wafer W is retained by the wafer transport section 101, the support region becomes slightly larger than the size of the wafer W, as illustrated in FIG. 19(b). That is to say, each wafer hold section 103 is disposed so that slight clearances are formed between the sidewalls 105 and the periphery of the wafer W.
However, since, as described above, a clearance is formed between each sidewall 105 and the periphery of the wafer W, when the wafer transport section 101 moves, inertial force makes the retained wafer W slide along the surface of the lower-surface support section 104, causing the periphery of the wafer to collide against the sidewall 105. This state is illustrated in FIG. 20(a). The collision wears the sidewall 105 and the lower-surface support section 104. FIG. 20(b) is a schematic representation of microscopic observation results on the sidewall 105 of the wafer transport section 101 used in an actual device, and reference number 108 denotes traces of the wear. Currently, coating/developing apparatus is significantly improved in throughput, with substrate transport devices being correspondingly increased in wafer transport speed. These increases in transport speed wear the wafer hold section 103 more easily.
In addition, coating/developing apparatus uses a variety of chemical liquids to conduct various types of processes upon the surface of the wafer W. These chemicals include, for example, the resist and developing solution described above, and a chemical for forming an anti-reflective film layer or protective film layer on the wafer W. During flow along the surface of the wafer, each such chemical is likely to turn around in a state of mist midway and adhere to, for example, the periphery or lower surface of the wafer. If such a chemical actually adheres to the wafer W being carried, each wafer hold section 103 may come into contact with the chemical and be chemically eroded. It should be noted that the chemical erosion includes corrosion.
These events, namely, the above-discussed physical wear and chemical erosion, may, for example, lead to a change in shape of the lower-surface support section 104 and result in the wafer W being retained askew. Wear on or chemical erosion of the sidewall 105 may cause the wafer W to enter traces of the wear or erosion, resulting in the wafer being supported in positionally shifted form with respect to a predetermined support region. If friction coefficients of the inclined section 106 and the lower-surface support section 104 increase as a result of the above wear and erosion, the wafer W could fail to slide downward from the inclined section 106. This failure could in turn lead to a fall of the wafer W from the wafer transport section 101 during carriage or result in abnormal processing of the wafer W due to possible transfer to the improper position in the required module.
In addition, each module of the coating/developing apparatus has a stage serving as a substrate support device and including a wafer lower-surface support section, and this stage may further have a position restriction section surrounding the periphery of the wafer W to prevent side slipping of the wafer mounted on the lower-surface support section. The mounting region, surrounded by the position restriction section, also has a size set to be larger than the wafer size, allowing for a dimensional error of the wafer W. As with the wafer hold section 103, the lower-surface support section and position restriction section of such a stage may suffer wear and the chemical erosion caused via the wafer W by a chemical. These events could cause the wafer W to be mounted or inclined in positionally shifted form with respect to the mounting region on the stage, and result in abnormal processing of the wafer W or in abnormal transfer thereof between the stage and the substrate transport device.
In Japanese Patent No. 3355950 (Paragraph 0017), although using a diamond-like carbon film to cover the surface of a resin-formed base for a machine part is described, problems associated with carriage and mounting of the substrate as discussed above are not described and thus the problems cannot be solved. In addition, in JP-11-243133-A (FIG. 7 and others), while the wafer transport section as discussed above is described, a technique for solving the above problems is not described.
Patent Document 1: JP3355950
Patent Document 2: JP-11-243133-A